Assume, instead, if the excellent professor had chosen a random beginning point (let's say, student number 21,058) from an enumerated list of every student in the UC system. He then chooses that student, as well as every 25th student after that (repeating the process with students 1 through 21,057), to be included in the sample. Which sampling strategy did he employ?

The sampling strategy described is called systematic sampling. In systematic sampling a researcher selects every nth participant from a list of the population after starting from a random point. In your scenario, the professor selects every 25th student starting from student number 21,058 in the UC system. After reaching the end of the list the professor continues the process from the beginning of the list until student number 21,057 is reached if necessary.

Here's how it would work step by step:

1. List all students in the UC system in some order ensuring that they are numbered (enumerated). 2. Randomly select a starting point (in this case, student number 21,058). 3. From that starting point select every 25th student (for example, student numbers 21,083, 21,108, 21,133, and so on) to be included in the sample. 4. If the end of the list is reached before the desired sample size is achieved circle back to the beginning of the list and continue the process until you have included every 25th student up to the point just before the starting point (in this case, up to student number 21,057).